Chemistery

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Atom = the smallest piece of matter which can exist on its own.

Element= substance made of the same type of atom.

Compound=Substance made of two or more different types of atoms joined together by chemical bonds.

= Chemical bonds are very strong therefore it is very difficult to split into elements.

Molecule = particle made of two or more atoms joined together by chemical bonds.

Mixture = made of two or more elements or compounds mixed together but not joined together by chemical bonds.

All mixtures can be separated by physical methods of separation. This is because there are no bonds between subatances.

solid dissolved in liquid (solid wanted)= crystallisation, evaporation

Solid dissolved in liquid (liquid wanted)= distillation

Insoluble solid in a liquid=filteration

two liquids mixed= chromotography, fractional distillation

two solids mixed = sieving, filter it

Mass of reactants = mass of products

elstron= no mass, charge 1-,position is the shell

neutron=mass is 1, has no charge, positioned in the nucleus

proton= mass 1, charge is 1+, positioned in the nucleus

Isotopes= atoms of the same element with the same number of protons but they will have a different number of neutrons.

electronic arrangement= 2,8,8,18

Group number = number of e on the outer shell

period number = total number of shells.

Chemical bonding

Atoms are chemically stable when their oter shell is full or empty.

To achieve stability atoms react with each other. Chemical reactions involve transfer of outer shell electrons.

Noble gases have full outer shell so they are already chemically stable. They are unreactive.We call them invert.: He, Ar, Ne.

Ionic bond forms between atoms of metal and non-metal.

Metals lose electrons to become POSITIVE IONS.

Non-metal always gain electrons to become NEGATIVE IONS.

Structure of ionic compurnds is called:

Giant ionic structure

Giant ionic lattice

The nature of ionic bonding:

Strong electrostatic sttraction between ions of oppisite charge.

Such attractions set in all directions within the giant ionic lattice.

Formulae of ionic compounds:

There are billions of ions of each type of charge in a lattice

We use the lowest whole number ratio of ions in the formula of ionic compund.

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Covalent bond= non-netal +non-metal

All non-metals need to gain electrons to achieve chemical stability.

When two non-metals reat they achieve it by sharing electrons.

Structure of covalent substances:

Most covalent compounds exist as molecules therefore type of structure: Simple Molecule

Nature of covalent bond: atoms share pairs of electrons.

Some molecules can be very large for example molecules of polymers (plastic).

Some covalent substances form GIANT COVALENT STRUCTURES or GIANT COVALENT LATTICES

eXAMPLES: DIAMOND, GRAPHITE ,SILICA.

Metallic bonding

Metal+metal

All metal lose outer shell electrons to the sea of delocalised electrons.

Structure: Giant metallic structure

Nature: Electrostatic attraction between positive metal ions and negative sea of delocalised electrons.

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Metals topic

Metal+oxygen=metal oxide

Metal + acid= salt + hydrogen

Rule of displacement

More reactive metal displaces the less reactive one from its compound.

All metal lose electrons during reactions to become stable and become positive ions.

The easier itis for a metal to lose its outer shell electrons the more reactive that metal is.

Group 1 metal is called alkali metals.

There are two products of reaction of metal with water :

flammable gas - hydrogen

alkaline substance - metal hydroxide

Metal + water = metal hydroxide + hydrogen

The reactions of group 2 metals become more reactive down the group.

Reaction of metals with acid

Metal + acid = salt + hydrogen

Salts form whe a metal displaces hydrogen from the acid.

All metal which are more reactive than H will react with acids (to displace H from it).

Not all metals can be reacted with acids.

Metals less reactive than H do not react with acids.

Most reactive metals (such as alkali metals) explode in acids.

Typical observations: fizzing, metal dissolves, test tube gets hot.

Extraction of metals and Reduction

Some metals are found NATIVE (pure, uncombined) e.g. gold, platinum,silver} very unreactive therefore do not combine with other elements.

Most metals are found in compounds

- they need to be extracted from them.

Ore = a rock which contains a metal or a metal compound in sufficent amount to make extraction profitable.

= method of extraction depends on reactivity of the metal

= most reactive metal form the strongest bonds(in compounds)

they are the most difficult to extract

Oxidation=oxygen is added

reduction= taking oxygen away

Copper can be found in an ore called malachite.

Oxidation and reduction in terms of electrons

Oxidation = loss of electrons

Reduction = gain of elctrons

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Oragnisation

Crude oil annatural gas are FOSSIL FUELS. This means that they are made of soft remains of dead sea creatures which fossilised millions of years ago.

Oil is less dense than water and moves up through the rock under the sea.

Crude oil is found in oil traps under the sea to get it by drilling.

Environmental consequences:

oil spills

marine habitats destroyed

visual pollution

Uses of crude oil:

to make many types of fuel

to make plastics

to make medicines

Crude oil is formed deep underground in sedimentary rock by the effect of heat and pressure on long dead plankton and other organisms.

Crude oil is a mixture oh hydrocarbons.

Hydrocarbons are compounds made of hydrogen and carbon ONLY.

Alkane is a saturated hydrocarbon.

formula for alkane: CnH2n+2

Methane = CH4

Ethane = C2H6

Propane = C3H8

Butane=C4H10

Properties of alkanes depends on the size of molecules.

The larger the molecules of alkanes (the more C-atoms):

-The higher their VISCOSITY

-The lower their FLAMMABILITY

-The higher their boiling points

-The lower their VOLATILITY

There are hundreds of hydrocarbons in crude oil. We divide them into groups called fractions.

Fraction = group of hydrocarbons of similar size and similar boiling points.

Refinery gases = fuel

Gasoline/petrol=fuel

naphtha=plastics

kerosene=jet fuel

diesel=fuel

lubricating oil= lubricants

fuel oil= guel for power stations/ factories

wax = grease/waxes/polishes

bitumen=asphalt

Different fractions have different boiling points. The larger the molecules the higher th b.p therefore we can separatefractions from crude oil by fractional distillation.

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Fractional distillation of crude oil

Separation of fractions is possible in a fractionating tower beacuse fractions have different b.p.

How does fractional distillation work?

crude oil is heated

most fractions evaporate/boil except bitumen which has v.high b.p.

fractionating tower is hot at the bottom and cool at the top

different fractions have different b.p so will condense at different levels.

the smaller the (molecules in) fraction 1. the lower the b.p 2.the higher up the tower it condenses

refining gas does not cendense.

H2 - burning splint gives squeaky pop test

CO2 - limewater goes cloudy

O2 - glowing splint relights

H2O VAPOUR - cobalt chloride paper goes from blue to pink

We burn fossil fuel for enery-they release heat ebergy on combustion-we convert it into electrical or kinetic energy.

Combustion = type of chemical reaction substance with oxygen.

Methane produces 2 products on combustion: CO2 AND H2O

Combustion reaction is a type of oxidation.

Problems with CO2

CO2 is a greenhouse gas which causes global warming

ice caps melting

sea levels rising

floods

climate change

Incomplete combustion of hydrocarbons

Happens when there is insufficent amount of O2 available

Instead of CO2-carbon monoxide form or carbon as soot

Unsaturated hydrocarbons

Alkenes = unsaturated hydrocarbons (they contain less than max number of H-atoms per molecule)

= tehy contain C = C double bond

Alkenes do not occur naturally in crude oil- they have to be manufactured in a process called CRACKING.

Alkenes are much more reactive than alkanes because they contain C=c double bond.

C=C double bond can break and extra atoms can be added to the molecules

This type of chemical reaction is called ADDITION. Addition is the most characteristic reaction of alkanes.

General formula of alkenes = CnH2n.